V4L/DVB (12703): gspca - sn9c20x: Reduces size of object

Use s16 instead of int where possible.
Use struct instead of arrays

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Brian Johnson <brijohn@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>